Wta. Harrison et al., SYNTHESES, CRYSTAL-STRUCTURES, AND PROPERTIES OF NEW LAYERED MOLYBDENUM(VI) SELENITES - (NH4)(2)(MOO3)SEO3 AND CS-2(MOO3)(3)SEO3, Inorganic chemistry, 33(26), 1994, pp. 6043-6049
The hydrothermal syntheses, single-crystal structures, and some proper
ties of two new layered molybdenum selenites, (NH4)(2)(MoO3)(3)SeO3 an
d Cs-2(MoO3)(3)SeO3, are described. These phases are built up from inf
inite, hexagonal tungsten bronze-like, anionic layers of MoO6 octahedr
a, capped on one side by pyramidally-coordinated Se atoms. The molybde
num-oxygen octahedra show an unusual distortion of the Mo atom towards
an octahedral face, resulting in a 3 short +3 long Mo-O bond distance
distribution within the MoO6 unit. Charge compensation is provided by
interlayer NH4+ or Cs+ cations. Powder X-ray, infrared, Raman and the
rmogravimetric data for these phases are also presented and discussed.
The M(2)(MoO3)(3)SeO3 (M = NH4, Cs) structure is related to, but dist
inctly different from the structure of NH4(VO2)(3)(SeO3)(2) recently r
eported. Crystal data: (NH4)(2)(MoO3)(3)-SeO3, M(r) = 594.85, hexagona
l, space group P6(3) (No, 173), a = 7.267(2) Angstrom, c = 12.031(3) A
ngstrom, V = 550.3(3) Angstrom(3), Z = 2, R = 3.26%, R(w) = 5.61% [559
observed reflections with I > 3 sigma(I)]; Cs-2(MoO3)(3)SeO3, M(r) he
xagonal, space group P6(3) (No. 173), a = 7.312(2) Angstrom, c = 12.37
7(2) Angstrom, V = 573.1(3) Angstrom 3, Z = 2, R = 5.93%, R(w) = 6.52%
[514 observed reflections with I > 3 sigma(I)].